Comparison of structural changes on enamel after er,cr:ysgg and 37% phosphoric acid etching- an esem analysis

Introduction: Tooth coloured restorations have evolved and so has the concept of bonding. A complete elimination of smear, microporosities and good wetting are the desirable substrate features which is mostly achieved by good enamel etching. Er,Cr: YSGG has shown a marked scope in enamel preparation and etching for bonded restoration.
Background: In the present study the conventional 37% phosphoric acid modality of etching is compared by ESEM analysis to Er,Cr:YSGG on enamel surfaces of extracted teeth.
Method: 40 anterior non diseased extracted teeth were collected and the coronal portion vertically sectioned by a diamond disc. The enamel specimens were then reduced to thickness of 1.0±0.5 mm and gauged by bur gauge. The specimens were then divided in GRE1 (control), GrE2 (acid etched) and GrE3 (Er,Cr:YSGG etched).These groups were then assessed for removal of smear layer and the predominant etching pattern exhibited.
Results: Chi-square test revealed that comparison of removal of smear layer in the two groups viz E2 & E3, did not differ significantly (p>.05). However in group E3, absence of smear layer was 88.9% which was significant (2= 5.44, p<0.05) at 5% level & in group E2 (2= 2.78) the removal of smear layer was significant at 10% level (p<0.10).For the two groups the absence of smear layer was 83.33% and it was significant (z= 2.80, p<0.01).In Type I etching pattern, the proportion in group E2 is higher and significant at 10% level (2= 2.78, 0.050.10) as compared to Group E3. In Type III etching pattern, the proportion in group E3 is higher & significant (2= 4.50, p<0.05) as compared to group E2.
Conclusion: Both 37% phosphoric acid and Er,Cr:YSGG were equally effective in smear layer removal from enamel specimens with no statistical significance. The predominant etching pattern seen under GrE2 was Type I and for GrE3 was Type III. The surface roughness was higher in laser treated surfaces. The present study advocates laser as an effective alternative to acid etching.